The oil sands deposits of northern Alberta, Canada are estimated to contain about 142 billion cubic meters (or 890 billion barrels) of bitumen, constituting the largest oil sands deposit in the world. Since the 1960s, bitumen recovered these deposits has been upgraded to make synthetic crude oil at production rates as high as one million barrels per day.
Bitumen is commonly recovered from the surface-mined oil sands ore using water-slurry-based extraction processes. Asphaltic acids, which are fractions of the bitumen asphaltenes present in bitumen and contain partly aromatic, oxygen-functional groups such as phenolic, carboxylic, and sulfonic types, become water-soluble, especially when the ore-water slurry's pH (i.e., acidity expressed as the minus logarithm of the hydrogen ion concentration: pH=−log [H+]) is slightly over 7, and act as surfactants reducing the surface and interfacial tensions. The reduction of surface and interfacial tensions in an oil sands ore-water slurry system causes disintegration of the ore structure and the resultant liberation of bitumen from the ore. Therefore, the water-soluble fractions of bitumen asphaltenes in oil sands play an important role in the recovery of bitumen from the surface-mined oil sands ore.
Recovery of bitumen from deep oil sands formations may be accomplished by thermal methods such as underground bitumen combustion (i.e., in situ combustion, or ISC), or steam injection methods such as steam-assisted gravity drainage (SAGD) and cyclic steam simulation (CSS). In these methods, the thermal energy injected into deep oil sands formations reduces the bitumen's viscosity and increases its mobility within the reservoir. Steam produced as an ISC by-product, or steam injected into a subsurface oil sands seam, condenses due to thermal energy losses and forms bitumen-water emulsions, which may be recovered by means of production wells. Water-soluble asphaltic acids also help the formation of the bitumen-water emulsions under in situ recovery conditions, since they act as surfactants reducing surface and interfacial tensions, thereby helping to break down the oil sands ore structure and promoting the release of bitumen from the ore.
If an emulsion is not sufficiently stable, the emulsified material (such as bitumen particles or droplets) will tend to flocculate or coalesce, leading to breakdown of the emulsion, which could hamper or preclude pipeline transportation of the emulsion. The production of surfactant species from bitumen asphaltenes would promote the formation of stable bitumen-water emulsions, thereby facilitating pipeline transportation of bitumen in the form of a bitumen-water emulsion.
For the reasons discussed above, there is a need for new methods for producing surfactants from bitumen asphaltenes to promote and enhance the formation of stable bitumen-water emulsions during both water-slurry-based and in situ processes for recovering bitumen from oil sands deposits, and thereby to improve bitumen recovery efficiency. There is a particular need for such methods which will result in reduced the amount of water required for water-slurry-based bitumen recovery processes. There is also a need for such methods which can make effective use of process waste products such as petroleum coke utilization flue gas. As well, there is a need for such methods which may be used in deep oil sands ore seams with the secondary beneficial effect of thermally insulating the ore seams, thus enhancing the efficiency of in situ thermal methods of bitumen recovery. There is a further need for new methods for producing surfactants which are also adaptable for use in association with bitumen-hydrocarbon mixtures and heavy crude oils. Further yet, there is a need for such methods which can be used over a wide range of temperatures and pH values. The present invention is directed to the foregoing needs.